Lithographic masks are exposed during a lithographic process to radiation thereby forming patterns on a wafer.
A lithographic mask error may result in a large number of defective wafers. Different mask errors may be associated with different costs.
On one hand there is a need to rigorously inspect lithographic masks as the cost associated with some lithographic masks error is high.
On the other hand the inspection of the lithographic process should be relatively fast.
There is a growing need to provide accurate and fast methods for inspecting a lithographic mask while taking into account the cost associated with mask errors.